The present invention relates a ring oscillation circuit of a MOS-IC which operates by undergoing only a small difference oscillation frequency in response to a wide range of power supply voltage level.
The present invention further relates to a non-volatile semiconductor memory integrated circuit (hereafter: EEPROM-IC) which is able to rewrite electrically, and especially to an EEPROM-IC which operates at a wide power source voltage range from low voltage and low power consumption with one power source. The present invention furthermore relates to electronic memory comprising an EEPROM-IC for storing information and powered by battery like solar battery, and especially to a small size and long life electronic memory. A ring oscillation circuit which in which plural odd invert circuits are connected in a ring configuration therein is used in conventional IC.
An EEPROM -IC with one power source, which generates a voltage several times that of the power source voltage for writing and erasing by driving a booster circuit using a ring oscillator is disclosed in Japan patent H05325578A.
As oscillation frequency of the conventional ring oscillation circuit varies greatly according to a change of input power, the variation being higher than is necessary. Thus current consumption of the circuit becomes large if a stable oscillation frequency at low voltage range is required such that the circuit operates over a wide power source voltage range.
In EEPROM with one power source, a voltage higher voltage than that of the power source is generated by a booster circuit by driving a ring oscillator. When the booster circuit is designed to operate at a low voltage like 1V, there is an increase in power consumption in the circuit at high power source voltage. Consequently, a large size solar battery is needed in an electronic device using an EEPROM-IC powered by solar battery. Electronic devices using a dry battery have a problem in that battery life is short.
The object of the present invention is to achieve stable oscillation by controlling the power source voltage of the oscillation circuit and limiting current.
Another object of the present invention is to provide an EEPROM-IC which does not increase its power consumption in accordance with an increase of power voltage at wide power source voltage range from low voltage to high voltage.
Further object of the present invention is to provide an memory which may be written to and erased using small size solar battery.